Liquid crystal display device and manufacturing method thereof

ABSTRACT

In order to prevent dielectric breakdown of TFT or an interlayer insulating film by static electricity with a reduced area at low cost, a liquid crystal display device has a configuration in which an interlayer insulating film and an a-Si film are formed in a display area and a control area inside terminals. Image signal lines and scan lines are insulated from each other through the interlayer insulating film and a-Si film in their intersections. On the other hand, only the interlayer insulating film is formed between static electricity protection lines and an earth line outside the terminals. When static electricity is induced, dielectric breakdown is caused to occur in the area outside the terminals. Thus, the display area and the control area are protected from the static electricity.

CLAIM OF PRIORITY

The present application claims priority from Japanese Patent ApplicationJP 2010-051862 filed on Mar. 9, 2010, the content of which is herebyincorporated by reference into this application.

FIELD OF THE INVENTION

The present invention relates to a display device, and more particularlyto a display device configured to prevent a reduction in the yield dueto dielectric breakdown by static electricity generated in themanufacturing process.

BACKGROUND OF THE INVENTION

In a liquid crystal display device, a TFT substrate and a countersubstrate are disposed opposite to each other with a liquid crystalinterposed between the two substrates. The TFT substrate is a substratein which pixels are arranged in a matrix form. Each of the pixelsincludes a pixel electrode, a thin film transistor (TFT), and the like.The counter substrate is a substrate in which color filters and the likeare formed at locations corresponding to the pixel electrodes of the TFTsubstrate. With this configuration, the liquid crystal display deviceforms an image by controlling the transmittance of light of the liquidcrystal molecules for each pixel.

There are various photolithography processes, in particular, in theformation of the TFT substrate of the liquid crystal display device.However, static electricity can easily be generated in thephotolithography processes such as film formation and drying using aspinner. In the TFT substrate, a large number of scan lines and imagesignal lines intersect each other through an interlayer insulation film.Further, a large number of TFTs are formed to control these lines. Whenstatic electricity is generated in the manufacturing process, theinterlayer insulation film is destroyed. As a result, a short circuitoccurs between the scan line and the image signal line, or the TFT isdestroyed. For this reason, the static electricity generated in themanufacturing process has a significant influence on the manufacturingyield.

In order to prevent the dielectric breakdown and TFT destruction causedby static electricity, measures are taken that prevent staticelectricity from entering a display area in which pixels and the likeare formed, for example, by allowing the static electricity to flow toearth before entering the display area. JP-A No. 203761/2008 describes aconfiguration that protects a scan line drive circuit and the likeprovided in the vicinity of the display area, from external staticelectricity. In this configuration, a conductive film is coated on thesurface of the scan line drive circuit and the like, and is groundedthrough an insulating film. Further, JP-A No. 21909/2001 describes anexample of a diode circuit for protection against static electricityproduced in the vicinity of the display area.

TFT using a-Si film is used in relatively large displays such as TVscreens. On the other hand, TFT using poly-Si is used in relativelysmall displays such as mobile phones and portable game consoles. In thecase of a liquid crystal display device using poly-Si TFT, the mobilityof poly-Si is high, so that a drive circuit is formed by the TFT. Then,a scan line GL drive circuit and the like are mounted in a substrate.

The large liquid crystal display device using the a-Si TFT and the smallliquid crystal display device using the poly-Si TFT are different in theconfiguration for protection against static electricity due to thedifference in the space of the substrate. The large liquid crystaldisplay device using the a-Si TFT has a relatively large space. Thus, adiode circuit is formed outside a display area 500 in which pixels arearranged in a matrix form, to protect the display area 500 from staticelectricity. FIG. 7 shows the circuit configuration.

In FIG. 7, a static electricity protection circuit is formed between thedisplay area 500 and a terminal 200 coupled to a scan line GL. In FIG.7, the static electricity protection circuit is formed using diode. Thediode is formed by coupling a gate and a drain or source of a TFT. InFIG. 7, when large positive static electricity enters from the terminal200, a diode 130 is turned on. When large negative static electricityenters, a diode 140 is turned on. This allows the static electricity toflow to earth, preventing destruction of the TFT in the display area500, or preventing dielectric breakdown of an interlayer insulating film300.

The small liquid crystal display device using the poly-Si TFT has asmall substrate. In addition, a portion of the drive circuit formed bythe TFT is mounted in the substrate. Thus, it is difficult to providethe static electricity protection circuit within the substrate. Such asmall liquid crystal display device is manufactured by the followingsteps. First, a large number of substrates are formed on a mother panel.Then, the substrates are separated from the mother panel by scribing orother means. In this way, individual liquid crystal display devices areformed.

Thus, in the small liquid crystal display device using the poly-Si TFT,a small space is formed between the individual substrates, in which astatic electricity protection circuit and the like are formed. At thetime of scribing, the small space is removed and discarded. Becauselarge static electricity is generated in the manufacturing process, thestatic electricity protection circuit is not used after completion ofthe product.

FIG. 8 shows the configuration of the static electricity protectioncircuit in the small liquid crystal display device described above. InFIG. 8, the substrate is located above a scribing line 210. Although thesubstrate includes the terminals 200 and the display area 500 or othercomponents, only one terminal is shown in FIG. 8.

In FIG. 8, a static electricity protection line 230 extends beyond thescribing line 210 to the outside of the substrate. The staticelectricity protection line 230 is coupled to a diode 150 as well as adiode 160. Each of the diodes 150 and 160 is formed by coupling a gateand a drain or source of the TFT. Here, it is assumed that large staticelectricity is induced in the vicinity of the terminal 200. The diodes150 and 160 are turned on to allow the static electricity to flow toearth. Thus, the TFT of the display area 500 or the interlayerinsulating film and the like in the substrate is protected from thestatic electricity.

However, the higher the resolution demanded in the display the more thenumber of pixels. As a result, the number of scan lines GL, the numberof signal lines DL and the like increase. For example, if the number ofscan lines GL increases, it is difficult to form the static electricityprotection circuit for each scan line GL in the limited space.

Meanwhile a selector driving method has been developed to address theincrease in the number of scan lines GL due to the increased resolution.The selector driving method is a method for dividing the scan lines GLinto a plurality of blocks, and scanning the scan lines GL for eachblock to reduce the number of leader lines of the scan lines GL.However, in the case of the selector driving method, the number ofcontrol TFTs increases to control the scan lines GL for each block. As aresult, it is necessary to have a space for the control TFTs. Thus, theproblem of lack of space for the static electricity protection circuitstill remains.

SUMMARY OF THE INVENTION

The present invention provides a configuration that can prevent the TFTor the interlayer insulating film 300 from being destroyed by staticelectricity, even if the number of pixels increases due to the increasedresolution.

The present invention overcomes the above problem by means described indetail below.

(1) There is provided a liquid crystal display device including asubstrate. The substrate includes a display area, a control areaadjacent to the display area, and terminals. In the display area, scanlines extend in a first direction and are arranged in a seconddirection. Further, image signal lines extend in the second directionand are arranged in the first direction. In addition, pixels are formedin each area surrounded by the scan lines and the image signal lines. Inthe control area, scan leaders coupled to the scan lines extend in thefirst direction and are arranged in the second direction. Further,control lines extend in the second direction and are arranged in thefirst direction. Then, the terminals are coupled to the control lines.An interlayer insulating film and an a-Si film are formed below theimage signal line in the display area and below a line formed in thesame layer as the image signal line in the control area. A line isformed in the same layer as the image signal line outside the terminal.The line is electrically coupled to the terminal. The interlayerinsulating film is formed below the line outside the terminal. However,the a-Si film is not formed below the line outside the terminal.

(2) In the liquid crystal display device described in (1), a width ofthe a-Si film is greater than a width of the image signal line, orgreater than a width of the line formed in the same layer as the imagesignal line in the control area.

(3) There is provided a method of manufacturing a liquid crystal displaydevice. The liquid crystal display device includes a substrate having adisplay area, a control area adjacent to the display area, andterminals. In the display area, scan lines extend in a first directionand are arranged in a second direction. Further, image signal linesextend in the second direction and are arranged in the first direction.In addition, pixels are formed in each area surrounded by the scan linesand the image signal lines. In the control area, scan leaders coupled tothe scan lines extend in the first direction and are arranged in thesecond direction. Further, control lines extend in the second directionand are arranged in the first direction. Then, the terminals are coupledto the control lines. The manufacturing method of the liquid crystaldisplay device includes the steps of: forming an interlayer insulatingfilm and an a-Si film below the image signal line in the display areaand below a line formed in the same layer as the image signal line inthe control area; forming a scribing line outside the terminal toseparate the substrate; forming an earth line in the same layer as thescan line outside the scribing line; forming the interlayer insulatingfilm outside the terminal, without forming the a-Si film on theinterlayer insulating film; forming a static electricity protection lineelectrically coupled to the terminal on the interlayer insulating film;forming the static electricity protection line so as to be coupled toother static electricity protection lines outside the earth line; andafter the above steps, separating the substrate along the scribing line.

(4) In the manufacturing method of the liquid crystal display devicedescribed in (3), a width of the a-Si film below the image signal linein the display area is greater than a width of the image signal line.The width of the a-Si film below a line formed in the same layer as theimage signal line in the control area is greater than a width of theline formed in the same layer of the image signal line.

(5) There is provided a liquid crystal display device includes asubstrate. The substrate includes a display area, and terminals forsupplying signals to the display area. In the display area, scan linesextend in a first direction and are arranged in a second direction.Further, image signal lines extending in the second direction and arearranged in the first direction. In addition, pixels are formed in eacharea surrounded by the scan lines and the image signal lines. Then, aninterlayer insulating film and an a-Si film are formed between the imagesignal line and the scan line in the display area. A line is formed inthe same layer as the image signal line outside the terminal. The lineis electrically coupled to the terminal. The interlayer insulating filmis formed below the line outside the terminal. However, the a-Si film isnot formed below the line outside the terminal.

(6) There is provided a method of manufacturing a liquid crystal displaydevice. The liquid crystal display device includes a substrate having adisplay area, and terminals for supplying signals to the display area.In the display area, scan lines extend in a first direction and arearranged in a second direction. Further, image signal lines extend inthe second direction and are arranged in the first direction. Inaddition, pixels are formed in each area surrounded by the scan linesand the image signal lines. The manufacturing method of the liquidcrystal display device includes the steps of: forming an interlayerinsulating film and an a-Si film below the image signal line in thedisplay area; forming a scribing line outside the terminal to separatethe substrate; forming an earth line in the same layer as the scan lineoutside the scribing line; forming the interlayer insulating filmoutside the terminal, without forming the a-Si film on the interlayerinsulating film; forming a static electricity protection lineelectrically coupled to the terminal on the interlayer insulating film;forming the static electricity protection line so as to be coupled toother static electricity protection lines outside the earth line; andafter the above steps, separating the substrate along the scribing line.

According to the present invention, it is possible to form a staticelectricity protection circuit without using a diode circuit. Thus, thespace for the static electricity protection circuit can be significantlyreduced. Further, according to the present invention, the staticelectricity protection circuit can be achieved in practice without usingany circuit element, resulting in a significant reduction in themanufacturing costs.

Furthermore, according to the present invention, it is possible tosignificantly reduce the space for the static electricity protectioncircuit. Thus, a high-resolution and highly reliable display with alarge number of pixels can be manufactured at low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of a liquid crystal display deviceaccording to the present invention;

FIG. 2 is a cross-sectional view in a scan line control area accordingto a first embodiment;

FIG. 3 is a cross-sectional view of the intersection between a staticelectricity protection line and an earth line according to the firstembodiment;

FIG. 4 is a cross-sectional view in the scan line control area accordingto a second embodiment;

FIG. 5 is across-sectional view of the intersection between the staticelectricity protection line and the earth line according to the secondembodiment;

FIG. 6 is a circuit diagram of the liquid crystal display device using aselector driving method;

FIG. 7 is an example of a protection circuit using diode; and

FIG. 8 is another example of the protection circuit using diode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described in detail withreference to preferred embodiments.

First Embodiment

FIG. 1 is a circuit diagram of a static electricity protection circuitaccording to the present invention. FIG. 1 shows only a portion of aliquid crystal display device. The liquid crystal display device shownin FIG. 1 uses a selector driving method. The selector driving methodcan reduce the number of lines for coupling between a scan line GL and ascan line GL drive circuit, compared to the conventional driving method.However, although it is possible to reduce the number of scan lines GLor the number of lines for controlling the scan lines GL, the number ofTFTs for controlling the scan lines GL increases. Hence protectionagainst static electricity is still an important issue.

Before describing the circuitry shown in FIG. 1, the selector drivingmethod will be described with reference to FIG. 6. In FIG. 6, a drivecircuit 1000 for scan lines GL and image signal lines DL is located onthe upper side of the figure. Then, a control area for driving the scanlines GL is located on the left side. In FIG. 6, the right side is adisplay area 500, in which pixels each including a pixel electrode 103,a pixel TFT 101, and the like, are arranged in a matrix form. In thedisplay area 500 in FIG. 6, the scan lines GL extend in the horizontaldirection and are arranged in the vertical direction. Further, the imagesignal lines DL extend in the vertical direction and are arranged in thehorizontal direction. In addition, the pixels are formed in each areasurrounded by the scan lines GL and the image signal lines DL.

The pixel TFT 101 is formed in each pixel. The drain of the pixel TFT101 is coupled to the image signal line DL. The gate of the pixel TFT101 is coupled to the scan line GL. The source of the pixel TFT 101 iscoupled to the pixel electrode 103. A liquid crystal layer 102 ispresent between the pixel electrode 103 and a common electrode 104. Aconstant voltage is applied to the common electrode 104, and a voltagecorresponding to an image signal from the image signal line DL isapplied to the pixel electrode 103. In this way, the orientation stateof the liquid crystal layer 102 is changed to control the transmittanceof light of the liquid crystal layer 102 for each pixel. Thus, an imageis formed.

The left side of FIG. 6 is the control circuit of the scan signal lines.In the conventional driving method, the same number of control lines ofthe scan lines GL as the number of scan lines GL should be provided onthe lower side of FIG. 6. Thus, it is necessary to have a large space toprovide the control lines of the scan lines GL. On the other hand, inthe selector driving method shown in FIG. 6, the scan lines GL aredivided into blocks to scan the scan lines GL for each block. Thus, thenumber of control lines of the scan lines GL is significantly reduced.

In FIG. 6, 72 scan lines GL constitute one block. In this specification,the scan line GL in the display area 500 is referred to as scan line GL,and the portion extending from the display area 500 to the outside inthe horizontal direction is referred to as scan leader GLL. The scanleader is coupled to the scan line GL in the display area 500. Then, afirst control TFT 111 and a second control TFT 121 are coupled to thescan leader GLL. On the left side of FIG. 6, 72 first control lines G1extend in the vertical direction. Similarly, 72 second control lines G2extend in the vertical direction. In addition, 36 first gate lines 112and 36 second gate lines 122, which are coupled to the second controllines G2, extend in the horizontal direction, respectively. Each scanline block containing 72 scan lines GL is selected by the first andsecond gate lines 112, 122.

As shown in FIG. 6, the 72 first control TFTs 111 are controlled at thesame time by the first gate line 112. Also, 72 second control TFTs 121are controlled at the same time by the second gate line 122. When thefirst control TFTs 111 are turned on, the second control TFTs are turnedoff. On the other hand, when the first control TFTs 111 are turned off,the second control TFTs 121 are turned on.

Here, for example, the top 72 scan lines GL are supposed to be a firstblock. When the first control TFTs 111 in the first block are turned on,the first control TFTs 111 in the second and subsequent blocks areturned off. Then, the scan lines GL in the second and subsequent blocksare in the off state during the scan of the scan lines GL in the firstblock.

When the scan of the first block is completed, all the first controlTFTs 111 in the first block are turned off. Then, the first control TFTs111 in the second block are turned on. Then, the scan lines GL in thesecond block are scanned. At this time, the scan lines GL in the firstblock and in the third and subsequent blocks are all in the off state.

It is to be noted that, for example, when the first control TFTs 111 inthe first block are turned on and when the scan lines GL in the firstblock are scanned, the second TFTs 121 are turned off. Thus, the scansignal is transmitted to the scan lines GL of the display area 500. Whenthe scan of the first block is completed and when the writing to thepixels existing in the first block is completed, the second control TFTs121 are turned on. Then, the scan lines GL are changed to VSS level.

As described above, also in the selector driving method, the scan of thescan lines GL is performed in the same manner as in the normal drivingmethod. In the normal driving, the necessary number of control lines forcontrolling the scan lines GL is, for example, 72×36=2592 lines.However, in the selector driving method, the necessary number of controllines is only 72×2=144 lines. For this reason, the number of controllines of the scan lines GL can be significantly reduced in the selectordriving method compared to the conventional method.

However, the selector driving method requires a large number of firstcontrol TFTs 111 and second control TFTs 121 in order to control thecontrol lines of the scan lines GL. For example, in FIG. 6, thenecessary number of first control TFTs 111 is 72×36=2592, and thenecessary number of second control TFTs 121 is 72×36=2592. The spaceoccupied by the first control TFTs 111 and by the second control TFTs121 is much smaller than the space for providing the control lines ofthe scan lines GL. However, the size of the substrate 100 is limited, sothat the problem of space arises when the number of pixels increases.

The present invention prevents the TFT or the interlayer insulating film300 from being destroyed by static electricity, only by theconfiguration of the static electricity protection lines 230 as shown inFIG. 1, without using the diode circuit as a circuit for protectingagainst static electricity. FIG. 1 is an enlarged view of the scan linesGL in the bottommost 36th block in FIG. 6, together with the terminals200, the scribing line 210, the earth line 220, and the staticelectricity protection lines 230. In other words, FIG. 1 is an enlargedview of the lower left portion of the liquid crystal display device. Itis to be noted that the particular potential VSS in FIG. 6 correspondsto the earth potential in FIG. 1.

In FIG. 1, the right side shows the display area 500 in which pixels arearranged in a matrix form. Each pixel includes the pixel TFT 101, thepixel electrode 103, the liquid crystal layer 102, the common electrode104, and the like. The scan leaders GLL extend from the scan lines GL ofthe display area 500 to the left side. Both of the first TFT 111 and thesecond TFT 121 are coupled to the scan leader GLL.

The 72 first control TFTs 111 are controlled by the second control lineG2 that transmits the 36th positive signal. The 72 second control TFTs121 are controlled by the second control line G2 that transmits the 36thnegative signal. When the first control TFTs 111 are turned on, thesecond control TFTs 121 are turned off. On the other hand, when thefirst control TFTs 111 are turned off, the second control TFTs 121 areturned on. The selector driving method is the same as described withreference to FIG. 6.

In FIG. 1, the 72 first control lines G1 extend in the verticaldirection. Similarly, the 72 second control lines G2 extend in thevertical direction. The first control TFTs 111 and the second controlTFTs 121 are coupled to the terminals 200 formed in an end portion ofthe substrate 100. The dotted line drawn on the outside of the terminals200 represents the scribing line 210. In other words, after completionof the substrate 100, the substrate 100 is separated from the motherpanel along the scribing line 210.

In FIG. 1, the earth line 220 is formed outside the scribing line 210 tosurround the scribing line 210. FIG. 1 only shows the lower left portionof the liquid crystal display device. However, actually, the earth line220 surrounds the entire circumference of the scribing line 210. Theearth line 220 is formed in the same layer as the scan line GL in thedisplay area 500.

Each of the static electricity protection lines 230 extends from eachterminal 200 beyond the scribing line 210 to the outside of the earthline 220. Then, each of the static electricity protection lines 230 iscoupled together outside the earth line 220. FIG. 1 shows a state inwhich the static electricity protection lines 230 are coupled to eachother outside the earth line 220. This is the state of the manufacturingprocess. After completion of the substrate 100, the portion outside thesubstrate 100 is removed along the scribing line 210. In this way, theterminals 200 are insulated from each other after completion of thesubstrate 100.

The static electricity protection line 230 is formed in the same layeras the image signal line DL in the display area 500. Thus, theinterlayer insulating film 300 is formed between the earth line 220 andthe static electricity protection line 230. In general, the interlayerinsulating film 300 is formed using SiN. For example, the lower lineformed in the same layer as the scan line GL, namely, the earth line220, is formed using MoW. Further, for example, the upper line formed inthe same layer as the image signal line DL, namely, the staticelectricity protection line 230, is formed by Al alloy.

In the area inside the terminals 200 in FIG. 1, namely, in the areaindicated by C in FIG. 1, the first and second control lines G1, G2,intersect the scan leaders GLL as well as the first and second gatelines 112, 122, through the interlayer insulating film 300 and the a-Sifilm 400. In the display area 500, the scan lines GL and the imagesignal lines DL intersect each other also through the interlayerinsulating film 300 and the a-Si film 400.

As described above, in the area inside the terminals 200, not only theinterlayer insulating film 300 but also the a-Si film 400 is providedbetween the upper and lower lines, to prevent short circuit in theintersections between the upper and lower lines. In other words, thea-Si film 400 undoped with impurities has a high electrical resistivity,and is the same as the insulation material. Thus, the a-Si film 400 hasthe same effect as the interlayer insulating film 300. In other words,in the intersection between the upper and lower lines, there is the sameeffect as forming two layers of the interlayer insulation film 300.

FIG. 2 is a view of the state described above. FIG. 2 shows, forexample, an A-A cross-sectional view of FIG. 1. In FIG. 2, the scanleader GLL, which is the lower line, extends in the horizontal directionon the substrate 100. The interlayer insulating film 300 is formed onthe scan leader GLL. The a-Si film 400 is formed on the interlayerinsulating film 300. Then, the first control line G1, which is the upperline, extends on the a-Si film 400 vertically on the paper. It is to benoted that the intersection between the scan line GL and the imagesignal line DL in the display area 500 has the same configuration asshown in FIG. 2.

The a-Si film 400 is slightly smaller than the first control line G1,extending below the first control line G1 in the same direction as thefirst control line G1. As shown in FIG. 2, the width of the a-Si film400 is greater by about w1=1 μm on one side, than the width of the firstcontrol line G1. Here, the thickness of the interlayer insulating film300 is, for example, about 200 nm. The thickness of the a-Si film 400is, for example, about 50 nm. The withstanding voltage between the upperline G1 and the lower line GLL is increased by the presence of the a-Sifilm 400 in the area inside the terminals 200, taking into account thecase in which a certain amount of static electricity enters the area.

While in the area outside the terminal 200, namely, in the areaindicated by D in FIG. 1, the earth line 220, which is the lower line,intersect each static electricity protection line 230, which is theupper line. The interlayer insulating film 300 is formed between theearth line 220 and the static electricity protection line 230. However,unlike the area C, the a-Si film 400 is not formed on the interlayerinsulating film 300 in the intersecting portion.

FIG. 3 is a view of the state described above. In FIG. 3, the earth line220, which is the lower line, extends in the horizontal direction on thesubstrate 100. The interlayer insulating film 300 is present on theearth line 220. Then, the static electricity protection line 230 extendson the interlayer insulating film 300 vertically on the paper. Only theinterlayer insulating film 300, but not the a-Si film 400, is presentbetween the earth line 220 and the static electricity protection line230.

When FIG. 2 and FIG. 3 are compared, the interlayer insulating film 300does not exist between the lower and upper lines in FIG. 3. Thus, whenstatic electricity enters, dielectric breakdown is more likely to occurin the configuration of FIG. 3 than in the configuration of FIG. 2. Inother words, when static electricity enters, dielectric breakdown occursin the intersection X between the earth line 220 and the staticelectricity protection line 230 in FIG. 1. This allows the staticelectricity to escape to the earth line 220. As a result, the controlarea formed in the area C in FIG. 1, as well as the interlayerinsulating film and the TFT in the display area 500, can be protectedfrom the static electricity.

As shown in FIG. 1, the feature of the present invention is to provideprotection against such static electricity only by the three-dimensionalwiring structure without using the diode circuit. As the presentinvention does not use the diode circuit, it is possible tosignificantly reduce the space for the protection circuit against staticelectricity. In addition, as the present invention does not use thediode circuit or the like and has a simple configuration, it is possibleto form the protection circuit at a low cost and to prevent themanufacturing yield from lowering due to the protection circuit.

Second Embodiment

There is also a process in which the interlayer insulating film 300 isslightly etched during etching of the a-Si film 400. FIG. 4 shows anexample of this case in FIG. 1. FIG. 4 shows a portion corresponding tothe A-A cross section of the area C inside the terminals 200 in FIG. 1.Further, FIG. 5 shows a portion corresponding to the B-B cross sectionof the area D outside the terminal 200 in FIG. 1.

In FIG. 4, the interlayer insulating film 300 keeps the original filmthickness below the a-Si film 400. However, in the portion not coveredwith the a-Si film 400, namely, in the portion indicated by 301, thethickness of the interlayer insulating film is smaller than the originalfilm thickness. However, in FIG. 4, the width of the a-Si film 400 isgreater than the width of the upper line. For this reason, thewithstanding voltage between the lower line GLL and the upper line G1 ishardly reduced.

FIG. 5 is a cross-sectional view of the intersection between the earthline 220 and the static electricity protection line 230 outside theterminal 200. In FIG. 5, the interlayer insulating film keeps theoriginal film thickness below the static electricity protection line230. However, in the portion other than the portion below the staticelectricity protection line 230, namely, in the portion indicated by301, the thickness of the interlayer insulating film is smaller than theoriginal film thickness. In FIG. 5, the thickness of the interlayerinsulating film 300 is reduced in an end portion of the staticelectricity protection line 230. Thus, the withstanding voltage isreduced in this portion.

As described above, using the process to slightly reduce the thicknessof the interlayer insulating film 300 during the etching of the a-Sifilm 400, the difference in the withstanding voltage further increasesbetween the area inside the terminal 200 in FIG. 1, namely, the area C,and the area outside the terminal 200 in FIG. 1, namely, the area D.

Thus, according to this embodiment, when static electricity isgenerated, the protection of the TFT or the interlayer insulating filmin the display area 500 and the control area can be further ensured.

The above description assumes that the liquid crystal display deviceuses the selector driving method, but the present invention is notlimited to this example. The present invention may also be applied to aliquid crystal display device having a configuration in which the lowerlines such as the scan lines GL, and the upper lines such as the imagesignal lines DL, intersect each other through the interlayer insulatingfilm 300.

Further, the above description assumes that the a-Si film 400 is formedon the interlayer insulating film 300 and below the upper lines in thedisplay area 500 and in the control area. However, the same effect canbe obtained when poly-Si is formed.

What is claimed is:
 1. A liquid crystal display device comprising asubstrate, wherein the substrate includes a display area, a control areaadjacent to the display area, and terminals, wherein the display areaincludes: scan lines extending in a first direction and arranged in asecond direction; image signal lines extending in the second directionand arranged in the first direction; and pixels each formed in an areasurrounded by the scan lines and the image signal lines, wherein thecontrol area includes: scan leaders extending in the first direction andarranged in the second direction, each of the scan leaders being coupledto one of the scan lines; first lines extending in the second directionand arranged in the first direction, each of the first lines beingcoupled to at least one of the scan leaders and intersecting a pluralityof others of the scan leaders which it is not coupled to, and secondlines extending to an edge of the substrate, wherein the terminals arecoupled to the first lines, at a first location which is away from theedge of the substrate, and are coupled to the second lines at secondlocation which is closer to the edge of the substrate than the firstlocation, wherein an interlayer insulating film and an a-Si film areformed below the first lines, wherein each of the first lines intersectsthe plurality of the other scan leaders to which it is not coupled viathe interlayer insulating film and the a-Si film, wherein the interlayerinsulating film is formed below the second lines, and wherein the a-Sifilm is not formed below the second line.
 2. The liquid crystal displaydevice according to claim 1, wherein a width of the a-Si film is greaterthan a width of a corresponding one of the first lines which it covers.3. The liquid crystal display device according to claim 2, wherein thea-Si film has a plurality of strips extending in the second direction,each of the strips is disposed respectively below one of the firstlines, and the interlayer insulating film is disposed below theplurality of strips.
 4. The liquid crystal display device according toclaim 1, wherein the scan lines intersect the image signal lines via theinterlayer insulating film and the a-Si film.
 5. The liquid crystaldisplay device according to claim 1, wherein the first and second linesare formed in the same layer as the image signal lines.
 6. The liquidcrystal display device according to claim 1, wherein the scan leadersare formed in the same layer as the scan lines.
 7. The liquid crystaldisplay device according to claim 1, wherein the substrate is separatedfrom a mother substrate along a scribing line which surrounds thesubstrate, the mother substrate has an earth line outside the scribeline, and third lines coupled to the second lines, the interlayerinsulating film is formed below the third lines, the earth lineintersects the third lines through the interlayer insulating film, andthe a-Si film is not formed below the third lines.
 8. A liquid crystaldisplay device comprising a substrate, wherein the substrate includes adisplay area, and terminals for supplying signals to the display area,wherein the display area includes: scan lines extending in a firstdirection and arranged in a second direction; image signal linesextending in the second direction and arranged in the first direction;and pixels each formed in an area surrounded by the scan lines and theimage lines, wherein the image signal lines intersect the scan lines viaan interlayer insulating film and an a-Si film in the display area,wherein the terminals are coupled to the scan lines at a first locationwhich is away from an edge of the substrate, and are coupled to firstlines at a second location which is closer to the edge of the substratethan the first location, wherein the first lines are formed in the samelayer as the image signal lines, and extend to the edge of thesubstrate, wherein the interlayer insulating film is formed below thefirst lines, and wherein the a-Si film is not formed below the firstlines.
 9. The liquid crystal display device according to claim 8,wherein the substrate is separated from a mother substrate along ascribing line which surrounds the substrate, the mother substrate has anearth line outside the scribing line, and second lines coupled to thefirst lines, the interlayer insulating film are formed below the secondlines, the earth line intersects the second lines through the interlayerinsulating film, and the a-Si film is not formed below the second lines.